1. Field of the Invention
The present invention relates to a miniature speaker device and a television set, and more particularly, it relates to a miniature speaker device and a television set each comprising a passive radiator.
2. Description of the Background Art
A speaker device comprising a passive radiator is known in general, as disclosed in Japanese Patent Laying-Open Nos. 11-150787, 2005-260625 and 9-70091, for example.
The aforementioned Japanese Patent Laying-Open No. 11-150787 discloses a speaker system comprising a main speaker (speaker), a passive radiator having a voice coil which is a drive system, a main amplifier (amplifier circuit) connected to the main speaker, a mixing amplifier connected to the main amplifier and mixing a signal for a center speaker and a signal for a subwoofer, and a motional feedback circuit connected to the passive radiator and amplifying sound pressure in frequency components of a low frequency range. This speaker system mixes the signal for the center speaker and the signal for the subwoofer, whereby the signal applied to the main speaker amplifies sound pressure of the mid frequency components in the mid and low frequency ranges. Thus, sounds generated from the main speaker are so formed that the sounds of the frequency components in the mid and low frequency ranges are amplified. Sounds generated from the passive radiator in resonance with the main speaker are so formed that sound pressure in the frequency components in the low frequency range is further amplified by the motional feedback circuit connected to the passive radiator.
The aforementioned Japanese Patent Laying-Open No. 2005-260625 discloses a speaker device comprising a cabinet (housing), a speaker unit (speaker) mounted on the cabinet, a passive radiator mounted on the same surface as the speaker unit (speaker) and a bass reflex duct coupled coaxially with the passive radiator and arranged inside the cabinet. This bass reflex duct of the speaker device has a first end coupled with an opening on a small diameter side of the passive radiator, to vibrate following vibration of the passive radiator. Consequently, the speaker device comprises effects as the passive radiator type speaker device and effects as the bass reflex type speaker device, thereby improving the acoustic characteristic in the low frequency range.
The aforementioned Japanese Patent Laying-Open No. 9-70091 discloses a speaker device comprising divided two enclosures (housings) to be fitted with each other, a speaker unit (speaker) arranged inside the enclosure, a passive radiator arranged at forward of the speaker unit and directed to the same direction as the speaker unit.
In the speaker system described in the aforementioned Japanese Patent Laying-Open No. 11-150787, however, the two signals for the center speaker and the subwoofer are needed in order to amplify the sounds of the frequency components in the mid and low frequency ranges. Thus, a circuit structure is disadvantageously complicated as compared with a case where a signal is input in order to input the two signals to the mixing amplifier. The motional feedback circuit must be provided on the passive radiator for amplifying sounds of the frequency components in the low frequency range, and hence the circuit structure is disadvantageously further complicated. The voice coil employed as the driving system and the like must be provided on the passive radiator in order to reflect feedback by the motional feedback circuit to the passive radiator, and hence the number of components are disadvantageously increased.
In the aforementioned speaker device described in the Japanese Patent Laying-Open No. 2005-260625, a member for amplifying the sound pressure in the frequency components in the low frequency range on the speaker unit is not provided, and hence the sound pressure in the frequency components in the low frequency range generated by the speaker unit is disadvantageously reduced. Thus, the sound pressure in the frequency components in the low frequency range is reduced also in the bass reflex duct and the passive radiator vibrating in resonance with the speaker unit, and hence it is conceivable that the sounds by the frequency components in the low frequency range are disadvantageously fully generated when the speaker device is downsized.
In the speaker device described in the aforementioned Japanese Patent Laying-Open No. 9-70091, only the passive radiator is provided, and hence the sounds by the frequency components in the low frequency range are disadvantageously fully generated when the speaker device is downsized.